Electric-motor regenerative pumps have heretofore been proposed and employed in automotive fuel delivery systems. Pumps of this character typically include a housing adapted to be immersed in a fuel supply tank with an inlet for drawing fuel from the surrounding tank and an outlet for feeding fuel under pressure to the engine. An electric motor includes a rotor mounted for rotation within the housing and connected to a source of electrical energy for driving the rotor about its axis of rotation. An impeller is coupled to the rotor for corotation therewith, and has a circumferential array of vanes around the periphery of the impeller. An arcuate pumping channel with an inlet port and an outlet port at opposed ends surrounds the impeller periphery for developing fuel pressure through a vortex-like action between the pockets formed by the impeller vanes and the surrounding channel. One example of a fuel pump of this type is illustrated in U.S. Pat. No. 3,259,072.
Fuel pumps of this character are subject to a number of design criteria for automotive applications. For example, the fuel pump may be required to deliver fuel at or above a minimum specified flow rate at specified pressure under nominal or normal operating conditions of temperature and battery voltage. The fuel pump may also be required to deliver a specified pressure and minimum flow under low battery voltage conditions, which may occur when it is attempted to start an engine at extremely low temperature. Another design requirement may be to deliver fuel at specified flow rate and minimum pressure under high temperature conditions in which vapor from the hot fuel can play a significant role. Design features and parameters intended to improve performance under some operating conditions can deleteriously affect operation under other conditions.
A general object of the present invention is to provide an electric-motor regenerative fuel pump of the described character that features improved performance under a variety of operating conditions, including normal operating conditions, cold starting conditions and hot fuel handling conditions as described above. Another object of the present invention is to provide a pump of the described character that is quiet, economical to manufacture and assemble, and achieves consistent and reliable performance over an extended operating lifetime.